This invention relates to pneumatic air valves and pneumatic air actuators. More particularly, this invention relates to ambient ports on pneumatic air valves and pneumatic air actuators.
Pneumatic air valves and actuators have long been used in aerospace applications, such as engine air starters in helicopters, due to their light weight, efficient packaging capability, and their ability to operate over a large temperature variation. Pneumatic air valves and actuators are designed to work against a reference pressure, the reference pressure generally being set at ambient pressure. Ambient ports are formed in the casing of pneumatic air valves and actuators to supply ambient air pressure to the reference sides of pneumatic air valves or actuators. Historically, pneumatic air valves and actuators have not incorporated filtration of the ambient ports.
As aerospace applications expand, so have the performance requirements of pneumatic air valves and actuators. Performance accuracy of pneumatic air valves and actuators depends upon tight control tolerances and small mechanical clearances. New applications have produced more challenging operating environments that expose the pneumatic air valves and actuators to increased external air contamination. Testing has revealed that unfiltered ambient ports allow ingestion of particles when the pneumatic air valves and actuators are subjected to external particles being driven at the unit. The ingested particles affect the performance of the pneumatic air valves and actuators by clogging the small mechanical clearances present in the pneumatic air valves and actuators. Though the use of filters on the ambient ports would prevent the ingestion of particles into the pneumatic air valves and actuators through the ambient ports, filters constrict the air flow through the ambient ports, impacting the reference pressure of the pneumatic air valves and actuators which impacts their performance. In addition, due to the amount of potential contaminate to which each pneumatic air valve unit is subjected, incorporating filtration is not considered a reasonable solution.